The advantage of producing antibodies in milk over the traditional source of antibodies from blood lies in the constancy of supply through the daily access to milk. After blood products are harvested, the production animal is allowed to recover for extended periods (for example, up to one month). Hence, the yield of antibodies is limited (approximately 3 to 30 mg per month) due to the finite amount of blood that can be obtained. In contrast, for example, dairy animals milked daily results in significant increases in yield (e.g. 2 mg per day multiplied by 30 days, gives 150 mg per month).
Injections or infusions directly into the teat of the mammal have previously been used to stimulate the production of antibodies in milk. Such examples are set out in the following literature: J. L. Smith, J. S Hogan & K. L Smith (1999) “Efficacy of intramammary immunization with an Escherichia coli JS bacteria.” Journal of Dairy Science, 82:2582-2588; J. S Hogan, K. L Smith, P. Schoenberger, S. Romig & L Thompson (1997) “Response of antibody titers to intramammary immunization with Escherichia coli JS bacteria.” Journal of Dairy Science, 80: 2398-2402; F. J Bourne, T. J Newby & J. W Chidlow (1975) “The influence of route of vaccination on the systemic and local immune response in the pig.” Research in Veterinary Science, 18:244-248. Such injections are time consuming as they must be repeated to re-stimulate antibody production. Furthermore, injection directly into the teat of a mammal frequently results in infections such as mastitis.
Intramammary immunization techniques have generally not been preferred as a route for vaccination under field conditions due to the high chance of mammary infection (R. F. Sheldrake (1987) Australian Journal of Dairy Technology, 42:30-32) and often requires application by highly skilled practitioners.
It should be noted that much of the published literature concerning immunoglobulin production in mammary gland secretions is directed to disease prevention (that is, vaccination) in animals or their offspring. Few are directed to the production of immunoglobulin enriched milk for the purposes of obtaining the immunoglobulins themselves.